A statement on its website said: "The bomb squad is investigating at the moment. This may have implications for air traffic in the form of cancellations and delays."

The Brussels-based main European air traffic control agency, Eurocontrol, posted on Twitter that passengers could expect "major delays."

The find comes only a day after experts in Munich triggered a controlled explosion of a 550-pound American WWII bomb in the center of Munich.

Police in Munich say experts successfully detonated the remains of a 550-pound bomb from the Second World War on Tuesday evening.

"A bomb disposal team with experts is presently assessing the situation, which will determine how long we will need to keep the section of the terminal closed," Cora Koopstra, from the airport's "action team," told NBC News.

The device was discovered at "Pier C," the wing of the terminal used mainly by flights to and from the European Union's passport-free Schengen zone. The terminal is a busy hub for European travelers and those connecting to Schengen destinations from international flights such as those from the U.S.

During World War II, Nazi Germany used the airport as a base for air raids on Britain. In 1943, the airport was destroyed by allied fighter aircraft; 400 tons of U.S. bombs were dropped on the complex.